Coating for building and bridges

External coating undergoes many harsh condition of environmental changes so it must have the property of UV resistant, anti-carbonation, breathability, waterproofness, crack bridge-ability, etc. Generally, coatings like on Acrylic elastomeric coating, Epoxy polyurethane paint system and Epoxy phenolic coating systems are proven as best.

IRC: SP-20, has clarified and put the specification requirement for Acrylic elastomeric coatings:

Coating requirement:

Sl No	Parameters	Requirement	Reference
1	Specific gravity	1.35 – 1.4	IS 345
2	Solid content	70 ± 3%	IS 345
3	UV resistant	No colour change	ASTM G 53 / DIN EN 150 – 105
4	IR Spectrum	As per Acrylic polymer	IR – Spectrum Meter standard
5	Adhesion with concrete	1.5 N/Sqmm	ASTM D 4541 -02 DIN 500014
6	Dry film thickness	200-225 micron per min 2 coats
7	Coverage	400-500 gm/Sqm for 2 coats
8	Physical properties diffusion resistance against carbon-dioxide	Equivalent to air thickness SD CO2 shall be > 50m	DIN 53122 Part 1
9	Diffusion resistance against water vapour	Equivalent to air thickness SD CO2 shall be > 4m	DIN 52615
10	Waterproofing characteristics	Percentage reduction in flux should be > 50%
11	Re-coat-ability	Min 2-72 Hrs or as per manufacturer specification with the approval of engineer in-charge

 

Primer requirement:

     a.       System – Single component

     b.       Base – Acrylic resin dispersion

     c.       Curing – Air cure

     d.       Colour – Milk white, transparent application

     e.       Shelf life: 6 months or as per manufacturer’s specification

     f.        Coverage – 75-100 Gms per Smtr (depending on surface porosity)

Performance guarantee of coating system: 5 years

Reference: IRC: SP-20 : 2008, page No 37 and 38.

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